The present invention relates to method and material for forming a pattern, and more particularly, it relates to a method for forming a resist pattern, used for forming a semiconductor device or a semiconductor integrated circuit on a semiconductor substrate, by using exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band and a pattern formation material used in the method.
Currently, in fabrication of a mass storage semiconductor integrated circuit, such as a 64 Mbit dynamic random access memory (RAM) and a logic device or a system LSI with a 0.25 xcexcm through 0.15 xcexcm rule, a resist pattern is formed by using a chemically amplified resist material including a polyhydroxystyrene derivative and an acid generator as principal constituents with KrF excimer laser (of a wavelength of a 248 nm band) used as exposing light.
Moreover, for fabrication of a 256 Mbit DRAM, a 1 Gbit DRAM or a system LSI with a 0.15 xcexcm through 0.13 xcexcm rule, a pattern formation method using, as exposing light, ArF excimer laser lasing at a shorter wavelength (of a 193 nm band) than the KrF excimer laser is now under development.
The chemically amplified resist material including a polyhydroxystyrene derivative as a principal constituent has high absorbance against light of a wavelength of a 193 nm band because of an aromatic ring included therein. Therefore, exposing light of a wavelength of a 193 nm band cannot uniformly reach the bottom of a resist film, and hence, a pattern cannot be formed in a good shape. Accordingly, the chemically amplified resist material including a polyhydroxystyrene derivative as a principal constituent cannot be used when the ArF excimer laser is used as the exposing light.
Therefore, a chemically amplified resist material including, as a principal constituent, a polyacrylic acid derivative or a polycycloolefin derivative having no aromatic ring is used when the ArF excimer laser is used as the exposing light.
On the other hand, as exposing light for a pattern formation method capable of coping with high resolution, X rays, an electron beam (EB) and the like are being examined.
When the X rays are used as the exposing light, however, there are a large number of problems in the exposure system and preparation of a mask. Also, when the EB is used as the exposing light, the throughput is disadvantageously low, and hence, the EB is not suitable to mass production. Thus, neither the X rays nor the EB is preferred as the exposing light.
Accordingly, in order to form a resist pattern finer than 0.10 xcexcm, it is necessary to use exposing light of a wavelength shorter than that of the ArF excimer laser, such as Xe2 laser (of a wavelength of a 172 nm band), F2 laser (of a wavelength of a 157 nm band), Kr2 laser (of a wavelength of a 146 nm band), ArKr laser (of a wavelength of 134 nm band), Ar2 laser (of a wavelength of a 126 nm band) and soft-X rays (of a wavelength of a 13, 11 or 5 nm band). In other words, a resist pattern is required to be formed by using exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band.
Therefore, the present inventors have formed resist patterns by conducting pattern exposure using F2 laser (of a wavelength of a 157 nm band) on resist films formed from conventionally known chemically amplified resist materials respectively including a polyhydroxystyrene derivative represented by Chemical Formula A, a polyacrylic acid derivative represented by Chemical Formula B and a polycycloolefin derivative represented by Chemical Formula C. 
Now, a method for forming a resist pattern by using any of the aforementioned conventional chemically amplified resist materials and problems arising in the conventional method will be described with reference to FIGS. 2A through 2D.
First, as shown in FIG. 2A, the chemically amplified resist material is applied on a semiconductor substrate 1 by spin coating and the resultant is heated, so as to form a resist film 2 with a thickness of 0.3 xcexcm. Thereafter, as shown in FIG. 2B, the resist film 2 is irradiated with a laser beam 4 through a mask 3 for pattern exposure. Thus, an acid is generated from the acid generator in an exposed portion 2a of the resist film 2 while no acid is generated in an unexposed portion 2b of the resist film 2.
Next, as shown in FIG. 2C, the semiconductor substrate 1 is heated with a hot plate at, for example, 100xc2x0 C. for 60 seconds.
Then, the resist film 2 is developed with an alkaline developer, thereby forming a resist pattern 5.
However, as shown in FIG. 2D, the resist pattern 5 cannot be formed in a good pattern shape, and there remains much scum on the semiconductor substrate 1. Such problems occur not only in using the F2 laser beam as the exposing light but also in using any of the other light of a 1 nm through 30 nm band or a 110 nm through 180 nm band.
Accordingly, a resist pattern cannot be practically formed by irradiating a resist film formed from any of the aforementioned chemically amplified resist materials with light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band.
In consideration of the aforementioned conventional problems, an object of the invention is forming a resist pattern in a good pattern shape by using exposing light of a 1 nm through 30 nm band or a 110 nm through 180 nm band with minimally producing scum.
The present inventors have studied the causes of the conventional problems occurring in using the conventional chemically amplified resist materials and have found the following:
First, the chemically amplified resist materials have high absorbance against light of a wavelength of a 1 nm through 180 nm band. For example, a resist film with a thickness of 100 nm formed from the chemically amplified resist material including a polyhydroxystyrene derivative has transmittance of 20% at most against a F2 laser beam (of a wavelength of a 157 nm band). Therefore, various examination has been made on means for improving the transmittance of a chemically amplified resist material against light of a wavelength of a lnm through 180 nm band. As a result, the transmittance of a chemically amplified resist material against light of a wavelength of a 1 nm through 180 nm band can be improved when a unit of a polymer having a cyano group (xe2x80x94Cxe2x89xa1N) on its side chain is introduced into a base polymer.
Furthermore, when any of the aforementioned chemically amplified resist materials, particularly the resist material including a polyhydroxystyrene derivative, is irradiated with light of a 1 nm through 180 nm band, a reaction is caused regardless of the function of an acid, so that a hydrogen atom bonded to carbon located at the xcex1-position of the principal chain of the polymer can be released and that polymer radicals from which the hydrogen atoms are released can bond to each other to be crosslinked. As a result, the solubility of an exposed portion of the resist film in a developer is degraded. Therefore, means for preventing the crosslinking reaction of the principal chains of the polymer of the chemically amplified resist material has been variously studied. As a result, it has been found that the crosslinking reaction of the principal chains can be avoided by substituting an alkyl group or a chlorine atom for a hydrogen atom located at the xcex1-position of the principal chain of the polymer.
Moreover, when a cyano group is introduced into a side chain of the polymer, the cyano group interacts with a hydroxyl group based on a hydrogen bond. Therefore, the dry etching resistance and the heat resistance of the resist film can be improved, and an unexposed portion of the resist film can be more effectively prevented from dissolving in a developer, so as to improve the contrast between the exposed portion and the unexposed portion of the resist film.
In addition, when a fluorine atom is introduced into an aromatic ring of the polyhydroxystyrene derivative, the transmittance against light of a wavelength of a 1 nm through 180 nm band can be improved, and the solubility in a developer of a hydroxyl group from which a protecting group is released can be improved. As a result, the contrast in the solubility between the exposed portion and the unexposed portion of the resist film can be improved.
The present invention was devised on the basis of the aforementioned findings, and specifically provides pattern formation materials and methods described below.
The first pattern formation material of this invention comprises a polymer including a first unit represented by Chemical Formula 1 and a second unit represented by Chemical Formula 2; and an acid generator: 
wherein R1 and R2 are the same or different and selected from the group consisting of an alkyl group such as a methyl group and an ethyl group, a chlorine atom and an alkyl group including a chlorine atom such as CCl3; R3, R4, R5 and R6 are a hydrogen atom or a fluorine atom, at least one of which is a fluorine atom; and R7 is a protecting group released by an acid.
In the first pattern formation material, since the first unit has a cyano group and the second unit has a fluorine atom, the transmittance against light of a wavelength of a 1 nm through 180 nm band is largely improved. Also, since an alkyl group, a chlorine atom or an alkyl group including a chlorine atom is substituted for each hydrogen atom located at the xcex1-positions of the principal chains of the first and second units, the principal chains are not crosslinked, resulting in improving the solubility of an exposed portion of the resist film in a developer. Furthermore, since the first and second units have a benzene ring, the dry etching resistance can be largely improved.
The second pattern formation material of this invention comprises a polymer including a first unit represented by Chemical Formula 3, a second unit represented by Chemical Formula 4 and a third unit represented by Chemical Formula 5; and an acid generator: 
wherein R1, R2 and R8 are the same or different and selected from the group consisting of an alkyl group such as a methyl group and an ethyl group, a chlorine atom and an alkyl group including a chlorine atom such as CCl3; R3, R4, R5, R6, R9, R10, R11 and R12 are a hydrogen atom or a fluorine atom, at least one of R3, R4, R5 and R6 being a fluorine atom; and R7 is a protecting group released by an acid.
In the second pattern formation material, since the first unit has a cyano group and the second and third units have a chlorine atom, the transmittance against light of a wavelength of a 1 nm through 180 nm band is largely improved. Also, since an alkyl group, a chlorine atom or an alkyl group including a chlorine atom is substituted for each hydrogen atom located at the xcex1-positions of the principal chains of the first, second and third units, the principal chains are not crosslinked, resulting in improving the solubility of an exposed portion of the resist film in a developer. Furthermore, since the second unit has a chlorine atom, the solubility in the developer of a hydroxyl group from which a protecting group is released can be improved. Accordingly, the solubility of the exposed portion of the resist film in the developer can be improved. As a result, the contrast in the solubility between the exposed portion and an unexposed portion of the resist film can be largely improved. Moreover, since the first, second and third units have a benzene ring, the dry etching resistance can be largely improved. In addition, since the third unit has a phenyl group, the wettability is improved so as to improve the adhesion to the substrate, and the dissolving rate in an alkaline developer can be controlled by adjusting the ratio of the third unit included in the polymer.
The third pattern formation material of this invention comprises a polymer including a first unit represented by Chemical Formula 6, a second unit represented by Chemical Formula 7 and a third unit represented by Chemical Formula 8; and an acid generator: 
wherein R1, R2 and R13 are the same or different and selected from the group consisting of an alkyl group such as a methyl group and an ethyl group, a chlorine atom and an alkyl group including a chlorine atom such as CCl3; R3, R4, R5 and R6 are a hydrogen atom or a fluorine atom, at least one of which is a fluorine atom; and R7 is a protecting group released by an acid.
In the third pattern formation material, since the first unit has a cyano group and the second unit has a fluorine atom, the transmittance against light of a wavelength of a 1 nm through 180 nm band is largely improved. Also, since an alkyl group, a chlorine atom or an alkyl group including a chlorine atom is substituted for each hydrogen atom located at the xcex1-positions of the principal chains of the first, second and third units, the principal chains are not crosslinked, resulting in improving the solubility of an exposed portion of the resist film in a developer. Furthermore, since the second unit has a fluorine atom, the solubility in the developer of a hydroxyl group from which a protecting group is released can be improved. Accordingly, the solubility of the exposed portion of the resist film in the developer can be improved. As a result, the contrast in the solubility between the exposed portion and an unexposed portion of the resist film can be largely improved. Moreover, since the first and second units have a benzene ring, the dry etching resistance can be improved. Also, since the third unit has a carboxyl group, carboxylic acid is generated in the exposed portion of the resist film through irradiation with light, resulting in improving the contrast between the exposed portion and the unexposed portion of the resist film.
The fourth pattern formation material of this invention comprises a polymer including a first unit represented by Chemical Formula 9, a second unit represented by Chemical Formula 10 and a third unit represented by Chemical Formula 11; and an acid generator: 
wherein R1, R8 and R14 are the same or different and selected from the group consisting of an alkyl group such as a methyl group and an ethyl group, a chlorine atom and an alkyl group including a chlorine atom such as CCl3; R9, R10, R11 and R12 are a hydrogen atom or a fluorine atom; and R15 is a protecting group released by an acid.
In the fourth pattern formation material, since the first unit has a cyano group and the second unit has a fluorine atom, the transmittance against light of a wavelength of a 1 nm through 180 nm band is largely improved. Also, since an alkyl group, a chlorine atom or an alkyl group including a chlorine atom is substituted for each hydrogen atom located at the xcex1-positions of the principal chains of the first, second and third units, the principal chains are not crosslinked, resulting in improving the solubility of an exposed portion of the resist film in a developer. Furthermore, since the second unit has a fluorine atom, the solubility in the developer of a hydroxyl group from which a protecting group is released can be improved. Accordingly, the solubility of the exposed portion of the resist film in the developer can be improved. As a result, the contrast in the solubility between the exposed portion and an unexposed portion of the resist film can be largely improved. Moreover, since the first and second units have a benzene ring, the dry etching resistance can be largely improved. Also, since the second unit has a phenyl group, the wettability is improved so as to improve the adhesion to the substrate. Furthermore, the dissolving rate in an alkaline developer can be controlled by adjusting the ratio of the second unit included in the polymer. In addition, since carboxylic acid is generated in the exposed portion of the resist film when an acid is generated through irradiation with light so as to release the protecting group from the third unit, the contrast between the exposed portion and the unexposed portion of the resist film can be improved.
Specific examples of the protecting group released by an acid represented by R7 in the aforementioned formulas are represented by Chemical Formula D: 
Also, specific examples of the protecting group released by an acid represented by R15 in the aforementioned formulas are represented by Chemical Formula E: 
The first pattern formation method of this invention comprises the steps of forming a resist film by applying, on a substrate, the first pattern formation material; irradiating the resist film with exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band for pattern exposure; and forming a resist pattern by developing the resist film after the pattern exposure.
In the first pattern formation method, since the first pattern formation material is used, the transmittance against light of a wavelength of a 1 nm through 180 nm band can be largely improved, the solubility of an exposed portion of the resist film in a developer can be improved, the dry etching resistance can be improved, and the contrast in the solubility between the exposed portion and an unexposed portion of the resist film can be largely improved.
The second pattern formation method of this invention comprises the steps of forming a resist film by applying, on a substrate, the second pattern formation material; irradiating the resist film with exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band for pattern exposure; and forming a resist pattern by developing the resist film after the pattern exposure.
In the second pattern formation method, since the second pattern formation material is used, the transmittance against light of a wavelength of a 1 nm through 180 nm band can be largely improved, the solubility of an exposed portion of the resist film in a developer can be improved, the dry etching resistance can be largely improved, and the contrast in the solubility between the exposed portion and an unexposed portion of the resist film can be largely improved. Furthermore, the wettability of the pattern formation material is improved so as to improve the adhesion to the substrate, and the dissolving rate in an alkaline developer can be controlled by adjusting the ratio of the third unit included in the polymer.
The third pattern formation method of this invention comprises the steps of forming a resist film by applying, on a substrate, the third pattern formation material; irradiating the resist film with exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band for pattern exposure; and forming a resist pattern by developing the resist film after the pattern exposure.
In the third pattern formation method, since the third pattern formation material is used, the transmittance against light of a wavelength of a 1 nm through 180 nm band can be largely improved, the solubility of an exposed portion of the resist film in a developer can be improved, the dry etching resistance can be largely improved, and the contrast in the solubility between the exposed portion and an unexposed portion of the resist film can be largely improved. Furthermore, since carboxylic acid is generated in the exposed portion of the resist film through irradiation with light, the contrast between the exposed portion and the unexposed portion of the resist film can be improved.
The fourth pattern formation method of this invention comprises the steps of forming a resist film by applying, on a substrate, the fourth pattern formation material; irradiating the resist film with exposing light of a wavelength of a 1 nm through 30 nm band or a 110 nm through 180 nm band for pattern exposure; and forming a resist pattern by developing the resist film after the pattern exposure.
In the fourth pattern formation method, since the fourth pattern formation material is used, the transmittance against light of a wavelength of a 1 nm through 180 nm band can be largely improved, the solubility of an exposed portion of the resist film in a developer can be improved, the dry etching resistance can be largely improved, and the contrast in the solubility between the exposed portion and an unexposed portion of the resist film can be largely improved. Furthermore, the wettability of the pattern formation material is improved so as to improve the adhesion to the substrate, and the dissolving rate in an alkaline developer can be controlled by adjusting the ratio of the second unit included in the polymer. Moreover, since carboxylic acid is generated in the exposed portion of the resist film through irradiation with light, the contrast between the exposed portion and the unexposed portion of the resist film can be improved.
In any of the first through fourth pattern formation methods, the exposing light is preferably F2 excimer laser, Ar2 excimer laser or soft-X rays.